The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Semiconductor processing involves various processes performed in a processing chamber. In these processes, heaters are used to maintain the wafer substrate to be processed at a targeted elevated temperature. The heaters may be implemented in various forms. For example, the heaters may be directly integrated into wafer processing chambers or the heaters may be used independently of other processing tools.
A heater generally includes a dielectric material that electrically insulates a resistive heating element that generates heat. Typical heaters used in the processing chambers can generally only operate at a temperature below 830° C. due to the limitations on the dielectric material. This is because the insulating strength of the dielectric material generally decreases with increased operating temperature. When the insulating strength of the dielectric material is weakened, dielectric breakdown will occur and short circuiting of the heater may result.
Moreover, leakage current increases exponentially as the temperature increases at a particular voltage. The increased leakage current, coupled with the reduced insulating strength of the dielectric material, increase the risk of leakage current flowing through ground, causing the heater to fail.
Further, the outer high emissivity protective surface of the heater may gradually degrade due to low partial pressure of oxygen environment and exposure to aggressive processing gases in the processing chamber. The degraded outer surface of the heater results in emissivity changes and decreased heat transfer from the resistive heating element, through the outer surface of the heater, to the surrounding environment. As a result, an internal temperature of the heater may become higher than an outer temperature of the heater, exacerbating weakening of the insulating strength of the dielectric material and increasing current leakage through the dielectric material.